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Chris Smith put the show panel to the test. Who will be The Naked Scientists' Big Brain of the Week? On team 1 - geneticist Patrick Short and astronomer Carolin Crawford. On team 2 - Ljiljana Fruk and Eleanor Drinkwater...

Chris - So the first one, this is round one, this is called a matter of time this round. So Carolin and Patrick which can live longer a shark or a tortoise?

Carolin - Are we allowed to confer on air? He’s whispering at me!

Patrick - Sorry I was whispering.

Carolin - We tend to think it's going to be tortoise...

Patrick - Maybe he’s tricking us.

Carolin - Yeah, and sharks also live pretty long, but I think I'm going to go for the tortoise because there’s one that lived over a century isn’t there? One of Darwin's tortoises?

Patrick - Yes I think I’m with you on that.

Chris - So are you going to go tortoise?

Carolin - Well giant tortoise, very specific, very long lived giant tortoises.

Chris - Well let’s find out!

Patrick - Aww I knew he was tricking us!

Chris - By carbon dating the eyeballs from dead specimens, scientists recently showed that Greenland sharks live for more than four hundred years. Female Greenland sharks are estimated to be at least 150 before they begin to reproduce. No you're quite right about the tortoises though Carolin because in the wild, giant tortoises do have a long lifespan. It’s at least 100 years or more. And in 2016, Jonathan the giant tortoise in the Seychelles was said to be the oldest living animal. He was more than 180 years old. So you didn't get any marks but you did show good knowledge. That's a good start. But perhaps you can do a bit of improvement in round two.

Team Two this is Ljiljana and Eleanor. Which lasts longer a day on Mars or a day on Venus. What do you think?

Eleanor - Can we answer the shark question instead?

Chris - Anyone would think we'd decided which questions to put to who.

Ljiljana - Wait, day on Mars?

Chris - Day on Mars or a day on Venus which is longer?

Eleanor - Which one’s bigger?

Chris - Well that’s the question Eleanor!

Ljiljana - I’d go with a day on Mars.

Eleanor - I like your definite answer, I trust you, you seem confident!

Ljiljana - Carolin is waving.

Chris - Carolin, why are they wrong?

Carolin - Because a day on Venus lasts longer than its year. So Venus goes once round in about two hundred forty odd Earth days, which is longer than it takes to go once round the sun which 225 days.

And a Sol, a Martian day we call a Sol, that's about the same length. It’s within half an hour or something of the day on Earth.

Chris - Thank you Carolin. I now don’t have to read the answer, which saves a bit of time.

Round two, animal magic, team one, Patrick and Carolin, which of these unattractive sounding animals is real and which one did we make up or are they both made up - the scrotum water frog or the bloated flatfish? What do you think?

Carolin - Don’t look at me! I'm sure somewhere in the universe there are planets where both exist, you know. You can't tell me unambiguously that none of them exist.

Patrick - So we have the scrotum water frog is that what you said?

Chris - Yes the scrotum water frog.

Patrick - And the bloated flatfish, you just wanted me to say those on air didn't you.

Carolin - We’ll take that as an assumed, yes, but it could be a double bluff.

Chris - What are you thinking then, the frog or the fish?

Carolin - I would go with the fish but I am not an expert.

Patrick - Okay, let’s say the frog is not real the fish is real.

Chris - So you’re going with the frog is made up?

Patrick - Yes.

Chris - No, the scrotum water frog lives in Lake Titicaca in the Andes. It's evolved a reduce lung capacity and it’s compensated by having very highly convoluted skin folds and I don’t why I’m looking at you Eleanor, you’re the biologist in the room.

These convoluted skin folds help it to breathe hence its name. And apparently these frogs do press ups on the bottom of a lake that creates disturbances in the water. This increases the delivery of oxygen which it then absorbs through it’s skin.

You're doing very well team, you've got zero. Okay back to Team two, see if you can improve on the score of zero overall so far. So Eleanor and Ljiljana, true or false, cats lack the ability to taste anything sweet?

Eleanor - Oh that's true. That's totally true.

Ljiljana - Yeah, I would go with Eleanor.

Eleanor - Because they did an experiment on lions in which they gave them the choice of water with sugar or water without sugar and apparently they couldn't tell the difference, or they behave similarly to both and so they assumed that they can’t taste sweet. The similar question which hasn't been tested, which I’m dying to test, but no one has let me do it yet, is can penguins taste fish? That's another question. No one knows.

Yes, you are off the bottom, you have one point. There are two genes which are used to make a working sweetness detector which is on the tongue. Cats lack a working version of one of them so they can't tell sweet from non sweet despite experiments like the ones you outlined there Eleanor where people have tried to get them to discriminate between sweet and non sweet things and they can’t do it. Very well done.

Back to Team One. You've got to save your rep here. It is all on this one. So this is called solve this, this round. This is a riddle slash a thought experiment which you got to work out what the answer to this is.

A cork dropped into a glass of water always drifts off to the side. So how can you make sure that the cork will always float in the center of the glass and to solve this riddle you only need glass, water and cork. What are you thinking?

Patrick - Do you have any of the Jeopardy music while we think?

Carolin - Do you have a cork? We could quickly experiment.

Patrick - So it always drifts to the side.

Carolin - How about you stir up the water before you drop the cork in and then you're not going to get motion out to the side of the glass.

Chris - No spoon provided, no fingers, just water.

Patrick - No fingers…

Carolin - How are we going to drop the cork in then?

Chris - With your mouth... no I don’t know. That’s not the answer I was thinking. It’s a good idea, but not the right answer.

Carolin - So I can't drink the water and then if…

Chris - It's got to float.

Patrick - Is it a normal glass, or can we change the shape of the glass in any way?

Chris - No, you get the same glass.

Patrick - Right. This is quite a conundrum yeah.

Chris - I am going to have to hurry you. Do you know the answer?

The answer is that you fill the glass right to the brim, because think about it, the surface tension means you'll pull the water into a curve, the cork always floats to the highest point in the water and the reason it goes off to the edge is because normally the water forms what's called a meniscus where the edge of the water is higher than the curved surface, which is why the cork goes there. Because of surface tension you can overfill the glass so it bulges above the rim and the cork will float to the top, dead center in the glass that way.

Patrick - That was pretty clever.

Chris - Yeah I'm glad you appreciate that. It's lovely. Right. No marks for you then. Right. You could be clinching it by the looks of things. Do you want to have a go anyway? It’s quite fun this one isn't it. So Eleanor and Ljiljana, this is purely just to show off now.

If you balanced a mop horizontally on your finger and you then cut the handle at the point where it was resting on your finger, so you effectively get two bits - you get a long bit of handle and then the short bit of handle with the mop head. Are you with me? If you weighed the two pieces - the short bit and the long bit - which would weigh more, the long bit or the short bit, or would they weigh the same?

Eleanor - If you could balance it… I feel like this is a trick question. This is a sneaky question. I feel like you want us to say the same, but I don't think it is. Is it something to do with mass and things? I don't know. Does it depend on the mop? What the mop is made of?

Chris - It’s a normal mop.

Are you going to say they weigh the same?

Eleanor - No no. It can't be the same because that’s too easy.

Chris - Same? Different? Going to have to hurry you.

Eleanor - I don't know. Maybe we should just go same.

Chris - You're saying same.

Unfortunately, you lost your edge right at the end. So what do you think? You've got an answer Patrick?

Patrick - The mop head is gonna be heavier.

Chris - Yeah I'd love to give you a bonus mark. No, I’m not going to let you get away with that one otherwise Carolin would've clinched it for you earlier wouldn't she? But the short bit actually weighs more. And this is why you have to put your finger so much closer to the mop head because there's a leverage effect. If you think about the length of the handle it's much lighter the long handle but because it's acting over a long distance there's a bigger torque. So it will actually weigh a lot less but it has a longer leverage. It's like Archimedes said if you give me a lever long enough and a place far enough away to stand I could lift the Earth. And that's the same principle. So actually it's a trick. It wouldn't weigh the same. The mop head plus a short bit of handle would actually weigh more.